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cyrus
13-Apr-2008, 21:04
One of the biggest hassles in alt processes is making a full-size positive which is then usually contact-printed using a uv light source. However, instead of making an enlarged positive and then contact printing it using the sun or a uv exposure unit, what would happen if you put a uv lightbulb in the enlarger, and then simply enlarging a negative as usual like you were making a "straight" print?

Ron Marshall
13-Apr-2008, 21:14
Unfortunately, the glass will absorb most of the UV, unless you are using a quartz enlarging lens.

cyrus
13-Apr-2008, 21:39
Unfortunately, the glass will absorb most of the UV, unless you are using a quartz enlarging lens.

Which glass? Don't contact print frames use glass too?

Donald Miller
13-Apr-2008, 21:41
It has been done before with Azo...which was and is (I guess that some still have it) very sensitive to UVA radiation. Jensen had a high wattage enlarger built to enlarge on Azo. Unfortunately Azo is much, much more sensitive than the alt processes. John Zdral had one of the Azo enlargers at one time...

Jensen (Durst Pro) had a Pt pd enlarger in the works at one time too...but I don't know that it ever reached production. As I recall the Azo enlarger had something like a 5KW lamp...read that to mean installing a new electrical main and new air conditioning.

Going on what Jensen said, according to his tests, the El Nikkor enlarging lenses did a pretty good job of passing UVA...much better than Rodenstock or Schneider. He went on to say that the Durst condensers (as in the 138 and the 184 did a pretty good job of passing UVA as well).

So yes it is possible but it requires something with a well selected light source and very high wattage to do what you want to do...the cost...priceless!!!

For your information, I converted my Durst 138 from the opal Thorn lamp (150 watt) to a lamp that approximates more closely a point light source and I designed it to use a 1200 watt lamp....this lamp requires a supplemental cooling fan for the lamp house and it allows very short and provides very sharp enlargements...much sharper than a conventional condenser/opal lamp configuration.

If I were going to do something along the lines of what you asked about, I would opt for a mercury or HID lamp and since these have a slow start characteristics, I would leave it on in a continual burn mode and use a shutter on the lens to control exposures.

John O'Connell
14-Apr-2008, 06:54
Well, there's a relatively long history to Pt/Pd enlargement:

http://www.usask.ca/lists/alt-photo-process/1996/alt96a/1087.html

You also might not need a much bigger lamp than the one used for the Azo enlargers, unless you really wanted a short exposure on the ferric-sensitized paper. It doesn't seem like a big deal if the exposure takes seven minutes on the enlarger for Pt.

The bigger issue I see for Pt enlarging is the potential focus shift from UVA to the visible range.

Nathan Potter
14-Apr-2008, 09:21
Seems that projection UV exposure would be possible for Pt/Pd. If UVA source is used, say around 365 nm line of a mercury lamp, there is some absorption in the condenser lenses and the imaging optics, esp. if the condensers are soda lime glass. But, so you may lose 50% of the light - you use a longer exposure. The heat from these lamps is pretty intense and might cook the conventional enlarger lamp house. They are high pressure gas filled lamps and are expensive. You may need a 250 to 500 watt version for reasonable exposures. Seems to me that you want to deliver 50 to 100 mW/cm2 to the exposing surface - but I'm only guessing. Don't know about the effect of such high optical flux on your negative! Don't worry about focus shift - you'll do focusing using the visible UV part of the emission spectrum (about 420 nm) and a bit of stray blue visible light. Just watch your eyes for damage from the reflected light and don't use a mirror focusing device unless you use protective glasses! Google for info on UV lamps for industrial use. Good thought!

Nate Potter

nolindan
14-Apr-2008, 10:29
a uv light bulb in the enlarger

The old Solar enlargers - the sort that used the sun and look a bit like an over sized Polaroid DayLab - might give you enough UV. But the sun isn't all that bright: solar radiation is only 1kW/Square meter. To get a printing time equivalent to a solar contact print would need a Fresnel condenser the size of the print being made. And then there is the issue of cooling the negative ...

Interesting thread on the subject on photo.net http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00G5lN.

Negative cooling would be a lot easier to handle if you used a 'Kokomo filter' before the negative so only the UV would get through.

Google will get you more.

cyrus
14-Apr-2008, 14:53
I have a platemaker, and you're right - the heat/radiation would frizzle my neg, melt my enlarger and burn out my eyes.
Oh well, worth a shot.

photographe_primitif
22-Dec-2019, 15:31
One of the biggest hassles in alt processes is making a full-size positive which is then usually contact-printed using a uv light source. However, instead of making an enlarged positive and then contact printing it using the sun or a uv exposure unit, what would happen if you put a uv lightbulb in the enlarger, and then simply enlarging a negative as usual like you were making a "straight" print?

I've been experimenting with UV light in an old Prinz 500 enlarger for a week. The results are promising. It works.

I shoot with antique cameras and usually make contact cyanotype prints. I wanted to enlarge without a separate digital negative process. I also started using a 35mm half frame camera (Universal Mercury II) and wanted to enlarge the half frames onto cyanotype. While it does take time for enough UV to pass through the glass optics, the only issue is the amount of time. Early tests required 5hr exposures with a 20w LED bulb.

I probably wouldn't have tried but for the lengthy explanations of why it couldn't be done!

Tin Can
22-Dec-2019, 16:19
+1.

Greg
22-Dec-2019, 16:38
When I was at RIT in the 1970s, I remember a professor and a few students attempted to construct an enlarger to use for alternative processes. They had the funds, and access to more equipment and technical expertise than most probably anyone of us could even wish for. Plus downstairs was a whole printing department who daily used high intensity UV light sources. I believe that the project was short lived for various technical reasons and problems.

Tin Can
22-Dec-2019, 17:18
I try to encourage experimentation

even now in post post post post foto

j.e.simmons
23-Dec-2019, 05:13
I tried it once with a CFL bulb in my Beseler 45MX enlarger. I only exposed for an hour and got a bit of an image on albumen. It does seem it would work with time.

Drew Wiley
23-Dec-2019, 14:54
UV enlargers have been commercially made. There are certain problems with bulbs bright enough to do the job quickly. There will be a lot of heat, potentially requiring a water jacket cooling system around the enlarger head. All the internal seals and gaskets have to be high-temp pure silicone, or the extreme UV will break them down rather quickly. And third, you have to protect your eyes with something like welding goggles. Sunburn risk too. It would be better to have a second, more ordinary bulb in place just for sake of focusing. The proprietary Fresson process uses a carbon-arc enlarger, a very old-fashioned option. Azo can be done with any reasonably strong halogen colorhead and a fast lens. CFL bulbs are just a bad joke all around, though I think specific UV ones are being made. See some of the older posts on this thread. As I recall, Jens did build his own prototype UV enlarger and put it up for sale, but ran into some legal issues safety-wise; it probably needed an automatic shroud to protect the operator from the light.

j.e.simmons
24-Dec-2019, 04:04
The photographer’s exposure to the light is an important consideration. I set a timer for all of my UV work and leave the darkroom during the exposure.

neil poulsen
25-Dec-2019, 00:48
I knew someone with such an enlarger, though I never saw it. It required a special quartz (I believe) enlarger lens. Indeed, he could print enlarged negatives onto pt/pd paper. But then, he began to use digital negatives.

Drew Wiley
27-Dec-2019, 10:53
Most EL Nikkor enlarging lenses are said to transmit UV better than other brands. But anything containing true quartz elements would have been very expensive to make, and no doubt quite rare now.

bnxvs
2-Jan-2020, 22:32
https://a4.pbase.com/o6/08/747708/1/131816753.K6TpA3x4.ELNikkor637580105mmtransk.png

Sevo
4-Jan-2020, 04:33
When working at a poster printer, we had a enlarger in the silkscreen lab for billboard and truck side prints - modified Klimsch, difficult device with a high power (upward of 5KW) arc lamp and watercooled head with exhaust pipes to the roof, needed modifiers into the coating, huge (up to A0) negatives and lots of time even at the resulting relatively modest enlargements. Only one person in staff could run it without creating mostly rejects. A smaller solution will probably have the same problems at a smaller scale (or even more, as the lamp power will be limited by the available cooling). Where full size negatives are feasible, it probably is not worth bothering.

Dr Klaus Schmitt
8-Jun-2020, 03:34
https://a4.pbase.com/o6/08/747708/1/131816753.K6TpA3x4.ELNikkor637580105mmtransk.png

If you use my work from my site which clearly states "All text and images carry my copyright and I do not allow to link to or copy / download from my site or any parts thereof without my prior permission." then AT LEAST quote my copyright!!

Dr Klaus Schmitt
8-Jun-2020, 03:38
I had been contacted a few years ago about such a solution for LF negatives using high powered 365nm UV LEDs in the enlarger head, but after some calculations decided to not go that way...

Dr Klaus Schmitt
8-Jun-2020, 04:16
I've been experimenting with UV light in an old Prinz 500 enlarger for a week. The results are promising. It works.

I shoot with antique cameras and usually make contact cyanotype prints. I wanted to enlarge without a separate digital negative process. I also started using a 35mm half frame camera (Universal Mercury II) and wanted to enlarge the half frames onto cyanotype. While it does take time for enough UV to pass through the glass optics, the only issue is the amount of time. Early tests required 5hr exposures with a 20w LED bulb.

I probably wouldn't have tried but for the lengthy explanations of why it couldn't be done!

I had been contacted about that a while ago, made some calculations and came out with several hours of needed exposure, so dropped that plan then.
Thanks for the confirmation!

Tin Can
8-Jun-2020, 04:57
Klaus, thank you for your considered views and experiments

Some are lax on Copyright

Quoting sources IS a problem as few were taught to do that

Dr Klaus Schmitt
8-Jun-2020, 05:08
Klaus, thank you for your considered views and experiments

Some are lax on Copyright

Quoting sources IS a problem as few were taught to do that

I'm admin in a large photo forum, there I would be issuing a 1st warning, 2nd would be removal of the poster ;-)

Dr Klaus Schmitt
8-Jun-2020, 05:13
Well, about the topic: today things ahev changes a bit, as high powered 365nm UV LEDs have gotten much cheaper and using some in a suitable condensor head would bring down exposure times considerably - IF and only IF a suitable UV passing lens would be used. THAT still is quite a challenge still, as many do not work. A suitable triplet lens with single or no coating would do, but would have to be stopped down - AND there is the focusing issue as those leses have considerable focus shift.

One would have to use some paper with fluorescent paint to focus on, then replace that with the photo sensitive paper and do teh exposure...

Pere Casals
8-Jun-2020, 05:40
Which glass? Don't contact print frames use glass too?

204528
http://photographyoftheinvisibleworld.blogspot.com/2011_01_16_archive.html


Coatings sometimes block UV, so depending on the lens version a difference may be there.


Probably a condenser type enlarger may be better for UV LEDs, as difusser type are way less efficient.

Tin Can
8-Jun-2020, 05:41
Very interesting and thank you for posting

Your links will be explored, over time


Well, about the topic: today things ahev changes a bit, as high powered 365nm UV LEDs have gotten much cheaper and using some in a suitable condensor head would bring down exposure times considerably - IF and only IF a suitable UV passing lens would be used. THAT still is quite a challenge still, as many do not work. A suitable triplet lens with single or no coating would do, but
woudl have to be stopped down - AND there is the focusing issue as those leses have considerable focus shift.

One would have to use some paper with fluorescent paint to focus on, then replace that with the photo sensitive paper and do teh exposure...

Dr Klaus Schmitt
8-Jun-2020, 05:54
204528
http://photographyoftheinvisibleworld.blogspot.com/2011_01_16_archive.html


Coatings sometimes block UV, so depending on the lens version a difference may be there.


Probably a condenser type enlarger may be better for UV LEDs, as difusser type are way less efficient.

Yes, but that used rather thin glass in contact frames transmits UV rather well, still

ic-racer
8-Jun-2020, 06:30
One of the biggest hassles in alt processes is making a full-size positive

I thought that was the easy part. I made some big negatives but gave up trying to make the platinum paper work right and went back to commercially produced silver paper.

bnxvs
8-Jun-2020, 21:46
If you use my work from my site which clearly states "All text and images carry my copyright and I do not allow to link to or copy / download from my site or any parts thereof without my prior permission." then AT LEAST quote my copyright!!
Where on this picture is indicated that it is not to be copied, cited, or otherwise used? Given that I found it in Google and I have no idea about your site - file a claim with Google. Or close your site from indexing by search engines.
And there is no need to scream like that - excessive emotions negatively affect health )))

koraks
9-Jun-2020, 02:00
Where on this picture is indicated that it is not to be copied, cited, or otherwise used?
That's not a valid argument. Copyright emerges at the moment the work is created, and it does not need to be explicitly indicated or filed for it to be present.

On the other hand, it is an entirely different matter if linking to an image on an external website is a violation of copyright. The problem here is that it is effectively a grey area and that litigation seems to have produced a variety of outcomes. I assume that Klaus is from Germany, and Germany seems to have upheld a fairly strict interpretation in which linking to an image can indeed be viewed as a violation of copyright. However, in other countries, other outcomes of similar cases exist.

I personally think it's reasonable to be somewhat flexible on both sides of the argument. Realistically, if you post an image on a website, there's the technical possibility that someone links to it. If you want to prevent this, then technical measures can be taken to prevent the image from being displayed on other domains. If a proper reference/citation is desired, it can be easily embedded into the image itself so that it is always displayed along with the image.
On the other hand, if someone complains about using their images without a proper reference, it doesn't hurt to include that reference. I mean, if that's all it takes...it's easy to do.

Tin Can
9-Jun-2020, 04:42
Interesting Copyright discussion

Here in middle USA, the local TV wants Digi files of specifically, NON-Professional HS grads, for Broadcast

Which does not solve the the Copyright issue...